The fluid catalytic cracking of hydrocarbons in modern refinery operations produces large amounts of C.sub.4.sup.- fuel gas containing light olefins of essentially no gasoline product value and the catalytic reforming of hydrocarbons produces large amounts of C.sub.6 to C.sub.8 aromatic hydrocarbons which though having value as gasoline blending stock are produced in excessive amounts. The petroleum refinery typically produces aromatics and light olefins on a mole ratio basis of aromatics to olefins of about 2:1 which is not suitable for directly carrying out a process for the alkylation of all of the aromatics that are produced.
The present invention particularly relates to a catalytic technique for alkylating C.sub.6 to C.sub.8 aromatics with light olefins to form heavier alkyl aromatic hydrocarbons. In particular, it provides a continuous process for alkylating C.sub.6 C.sub.8 aromatics, particularly benzene, contained in a catalytic reformate with ethene and propene contained in C.sub.4.sup.- fuel gas to form C.sub.1 to C.sub.4 alkyl substituted aromatic hydrocarbons for use as gasoline blending stock. Ethene containing gases, such as petroleum cracking offgas, and catalytic reformate containing, for example, benzene, toluene, xylene and ethyl benzene are useful feedstocks for the process.
Developments in zeolite catalysis and hydrocarbon conversion processes have created interest in utilizing olefinic feedstocks for producing C.sub.5.sup.+ gasoline, diesel fuel, etc. In addition to basic chemical reactions promoted by ZSM-5 type zeolite catalysts, a number of discoveries have contibuted to the development of new industrial processes. These are safe, environmentally acceptable processes for utilizing feedstocks that contain lower olefins, especially C.sub.2 -C.sub.4 alkenes and feedstocks containing aromatic compounds, especially C.sub.6 to C.sub.8 aromatics.
Chen U.S. Pat. No. 3,729,409 discloses improving the yield-octane number of a reformate by contacting the reformate in the presence of hydrogen over a zeolite catalyst. Garwood et al U.S. Pat. No. 4,150,062 discloses a process for the conversion of C.sub.2 to C.sub.4 olefins to produce gasoline which comprises contacting the olefins with water over a zeolite catalyst. The Haag et al U.S. Pat. No. 4,016,218 and Burress U.S. Pat. No. 3,751,506 disclose processes for the alkylation of benzene with olefins over a ZSM-5 type catalyst. The Heroute et al U.S. Pat. No. 4,209,383 discloses the catalytic alkylation of benzene in reformate with C.sub.3 -C.sub.4 olefins to produce gasoline.
It has now been found that contacting a catalytic reformate feed comprising C.sub.6 to C.sub.8 aromatic hydrocarbons with a light olefin gas feed, comprising ethene, propene and/or butene at a weight ratio of aromatics to olefin of 10:1 to 15:1, over a zeolite catalyst that the C.sub.6 to C.sub.8 aromatics in the catalytic reformate can efficiently be converted to alkyl aromatic hydrocarbons which are suitable for use as gasoline blending stocks.
In accordance with the present invention refinery olefins and light aromatic hydrocarbons are upgraded to products of higher value in a practically most efficient manner.